<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<title>浮动元素的破坏性</title>
	<style type="text/css">
		.top_bar{
			border: 1px solid red;
		}
		.child1{
			width: 200px;
			height: 200px;
			background-color: green;
			float: left;
		}
		.child2{
			width: 200px;
			height: 200px;
			background-color: orange;
			float: right;
		}
		.header{
			width: 100%;
			height: 100px;
			background-color: purple;
		}
	</style>
</head>
<body>
	<div class="top_bar">
		<div class="child1">儿子</div>
		<div class="child2">二儿子</div>
	</div>
	<div class="header">
		
	</div>

</body>
</html>